Modified cold-bonded ball for reducing metallic iron in vanadium slag obtained by extracting vanadium from converter as well as preparation method and application of modified cold-bonded ball

Abstract

The invention discloses a modified cold bonding ball for reducing metallic iron in converter vanadium extraction vanadium slag and a preparation method and application thereof, and belongs to the technical field of ferrous metallurgy. The modified cold-bonded pellets contain Na2O and F <-> in a specific ratio, and low-calcium and low-silicon impurities are strictly controlled. The preparation method comprises the following steps: mixing, briquetting and naturally air-drying the raw materials including the iron oxide scale, the vanadium extraction sludge, the regenerated cryolite and the binder. During application, 2-3 furnaces are taken as a vanadium extraction-deslagging period, the modified cold solid ball is added into a deslagging furnace, and the melting point and the viscosity of vanadium slag are remarkably reduced through the powerful slagging effect of the modified cold solid ball, so that slag-iron separation is promoted. According to the method, the content of total iron and metallic iron in the vanadium slag can be stably and effectively reduced, iron loss is reduced, and the grade of the vanadium slag is improved.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy technology, specifically relating to a modified cold-solidified pellet for reducing metallic iron in vanadium slag from converter vanadium extraction, its preparation method, and its application. Background Technology

[0002] In the vanadium extraction process in a converter, vanadium-containing molten iron is oxidized and enriched in the slag during oxygen blowing, forming vanadium slag. To promote vanadium oxidation, the slag at the end of the blowing process typically contains a high concentration of FeO, and the intense stirring causes a large number of metallic iron beads to be entrained in the slag phase. This results in a high total iron (TFe) and metallic iron (MFe) content in the final vanadium slag, which not only leads to iron loss and increases steelmaking costs, but also affects the efficiency of subsequent vanadium extraction processes and the grade of vanadium products.

[0003] In existing technologies, adding slag conditioners (such as ferrosilicon and sodium salts) at the end of the blowing process often improves slag fluidity and promotes iron bead separation. However, ferrosilicon is expensive and increases the silicon content in vanadium slag, affecting vanadium recovery rates in subsequent processes; while sodium salts are cheaper, they increase the phosphorus content in vanadium slag, affecting the quality of vanadium products. Other technical solutions focus on using calcium-containing materials (such as lime and calcium-rich sludge) as coolants or modifiers to reduce iron loss by increasing the CaO content in the slag. However, excessively high CaO content can negatively impact subsequent vanadium slag treatment (e.g., it is detrimental to the sodium vanadium extraction process). Furthermore, conventional coolants or modifiers often have limited functionality and fail to effectively synergize with the vanadium extraction process, resulting in unstable iron reduction effects and limited room for improvement.

[0004] Therefore, developing a comprehensive technical solution that is cost-effective, can be deeply integrated with the vanadium extraction process, and can significantly reduce the metallic iron content in vanadium slag is of great practical significance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a novel modified cold solid ball for vanadium extraction in converters, so as to overcome the shortcomings of existing vanadium extraction coolants or slag conditioners in reducing the metallic iron content of vanadium slag.

[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows.

[0007] In a first aspect, the present invention provides a modified cold-solidified pellet for reducing metallic iron in vanadium-containing slag from a converter, wherein the chemical composition of the modified cold-solidified pellet, based on the total mass of the pellet, satisfies: TFe ≥ 50%, Na₂O 3.0~6.0%, F - ≥1.0%, CaO≤1.5%, SiO2≤7.5%, S≤0.1%.

[0008] Furthermore, the particle size of the modified cold-solidified spheres is 30~50mm.

[0009] Secondly, the present invention provides a method for preparing the above-mentioned modified cryo-balls: 65.0 to 80.0 parts by weight of iron oxide scale, 5.0 to 15.0 parts by weight of vanadium extraction sludge, 3.0 to 4.0 parts by weight of recycled cryolite and 1.5 to 2.5 parts by weight of binder are mixed, pressed and cured to obtain the modified cryo-balls.

[0010] Furthermore, the CaO content in the iron oxide scale is ≤0.5% by mass, and its particle size is ≤5mm.

[0011] Furthermore, the vanadium extraction sludge contains ≥60% TFe, ≤0.5% CaO, ≤0.1% P, and ≤30% H2O by mass.

[0012] Furthermore, the regenerated cryolite contains ≥45% F by mass, ≥29% Na2O by mass, ≥25% Al2O3 by mass, ≤0.5% H2O by mass, and has a particle size ≤3mm.

[0013] Furthermore, the binder is one that enables the raw materials to be bonded and formed, and it itself does not introduce impurities that are harmful to the subsequent vanadium extraction process into the modified cold-fixed spheres.

[0014] Furthermore, the curing process involves natural air drying for 4-5 days, resulting in a moisture content of ≤3.0% and a pulverization rate of ≤10% for the obtained modified cold-fixed balls.

[0015] Thirdly, the present invention provides a method for reducing metallic iron in vanadium slag from a converter: vanadium extraction is performed in a cycle of 2 or 3 consecutive heats, wherein the last heat of the cycle is a slag-discharging heat and the remaining heats are non-slag-discharging heats; in the non-slag-discharging heats, pig iron blocks and ordinary chilled pellets are added to the converter and pure oxygen blowing is performed, and steel is tapped after blowing is completed while slag is retained; in the slag-discharging heats, without adding pig iron blocks, waste slag, or other metallic materials, the aforementioned modified chilled pellets are added to the converter and pure oxygen blowing is performed, and semi-steel is discharged first after blowing is completed, and then the vanadium slag is poured out.

[0016] Furthermore, in the non-slag-discharging furnace batches, the amount of pig iron blocks added is 6 to 8 tons per furnace; the amount of ordinary chilled pellets added is 15 to 35 kg / ton of molten iron.

[0017] Furthermore, the final blowing temperature of the non-slag-discharging furnace is controlled at 1360~1400℃.

[0018] Furthermore, in the slag-removing furnace, the amount of modified chilled pellets added is 25-45 kg / ton of molten iron, and all of them should be added within 3 minutes after the start of oxygen blowing.

[0019] Furthermore, the blowing process of the slag-discharging furnace meets the following requirements: oxygen lance position 1.6~2.0m; bottom-blown gas is nitrogen, with a flow rate of 60~100 Nm³. 3 / h; oxygen supply pressure 0.68~0.85MPa, oxygen supply flow rate 16800~18500Nm 3 / h; oxygen blowing time 3.5~9.0 minutes; control the final blowing temperature to 1380~1410℃.

[0020] The beneficial effects of this invention are as follows: The modified cold-solidified pellets and their application method provided by this invention can effectively reduce the total iron and metallic iron content in vanadium slag from converter vanadium extraction, significantly reduce iron loss during the vanadium extraction process, and thus reduce production costs. These modified cold-solidified pellets use industrial solid waste such as iron oxide scale and vanadium extraction sludge as main raw materials, and select recycled cryolite as the core functional additive. While achieving resource recycling and possessing both environmental and cost advantages, the synergistic effect of components such as Na and F can effectively improve the fluidity of vanadium slag and promote slag-iron separation. Furthermore, by combining the modified cold-solidified pellets with the above-mentioned specific components with a "periodic vanadium extraction-slag dumping" operation system, and adding them in concentrated batches during slag removal, the physicochemical properties of the final slag can be significantly optimized while ensuring the quality of semi-steel and the efficiency of vanadium extraction. This not only allows for stable control of the iron content in the vanadium slag but also facilitates the acquisition of high-quality vanadium slag with more stable composition and lower levels of impurities such as phosphorus and potassium, creating favorable conditions for subsequent vanadium extraction. The entire solution is well-suited to the existing converter vanadium extraction process, with clear operating logic and well-defined parameters, making it easy to implement and stably control in production, and has significant prospects for industrial application. Detailed Implementation

[0021] To make the technical problems, solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with the embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as understood by one of ordinary skill in the art.

[0022] This invention provides a method for reducing metallic iron in vanadium extraction slag from a converter, wherein the vanadium extraction operation is performed in a cycle of two or three consecutive heats; wherein the last heat of the cycle is defined as the slag-discharging heat, and the remaining heats are defined as non-slag-discharging heats; the specific steps are as follows: (1) Non-slag-tapping furnace operation: Add pig iron blocks (6-8 tons per furnace) and ordinary chilled pellets (15-35 kg / ton of molten iron) to the converter and carry out pure oxygen blowing. Control the blowing endpoint temperature to 1360-1400℃. After the blowing is completed, perform the tapping operation and retain the slag in the converter to provide a slag-forming basis for the next furnace.

[0023] In this invention, the "ordinary chilled pellets" refer to iron-containing chilled pellets commonly used in the field for temperature control during the vanadium extraction process in converters. The mass content of TFe in the ordinary chilled pellets is ≥60%, and there are no specific requirements for slag conditioning components such as Na and F.

[0024] (2) Slag removal furnace operation: No pig iron blocks, waste slag and other metal materials are added in this furnace. Modified chilled pellets are added to the converter at a rate of 25-45 kg / ton of molten iron, and all pellets should be added within 3 minutes after the oxygen blowing starts.

[0025] Following this, pure oxygen blowing is performed, with the key process parameters controlled as follows: oxygen lance position 1.6~2.0m, bottom blowing gas is nitrogen and the flow rate is controlled at 60~100 Nm³. 3 / h, oxygen supply pressure 0.68~0.85 MPa, oxygen supply flow rate 16800~18500 Nm 3 The oxygen blowing rate is 3.5~9.0 minutes per hour. The final blowing temperature is controlled at 1380~1410℃. After blowing, the semi-steel is discharged first, and then the vanadium slag is poured out, resulting in vanadium slag with a significantly reduced iron content.

[0026] In a preferred embodiment of the present invention, the modified cold-fixed spheres are prepared by the following method: Weigh out 65.0~80.0 parts of iron oxide scale (with CaO content ≤0.5% and particle size ≤5mm), 5.0~15.0 parts of vanadium extraction sludge (with TFe content ≥60%, CaO ≤0.5%, P ≤0.1%, and H2O ≤30%), 3.0~4.0 parts of recycled cryolite (with F content ≥45%, Na2O ≥29%, Al2O3 ≥25%, H2O ≤0.5%, and particle size ≤3mm), and 1.5~2.5 parts of binder (at least one of silicate cement, aluminate cement, bentonite, and water glass).

[0027] After the above raw materials are mixed evenly, they are pressed into pellets with a particle size of 30-50 mm using a briquetting machine. The shaped pellets are then placed in a ventilated area to air dry naturally for 4-5 days until the moisture content of the finished pellets is ≤3.0% and the breakage rate is ≤10%, thus obtaining modified cold-cured pellets with sufficient strength. Based on the total mass of the finished product, its key chemical components meet the following requirements: TFe ≥ 50%, Na₂O 3.0-6.0%, F… -≥1.0%, CaO≤1.5%, SiO2≤7.5%, S≤0.1%.

[0028] The binder described in this invention, while imparting sufficient bonding strength to the finished spheres (ensuring a sphere breakage rate ≤10%), does not introduce any impurities into the modified cold-solidified spheres that would adversely affect subsequent vanadium extraction processes. In actual production, the specific components of this binder can be flexibly adjusted according to product quality requirements. Any binder that meets the aforementioned dual requirements of bonding strength and impurity control is suitable for this invention.

[0029] In this invention, the modified cryo-solidified pellets are key to reducing metallic iron in vanadium slag. They use recycled cryolite (Na3AlF6) as an additive, simultaneously providing Na2O and F at high temperatures. - Na₂O can effectively lower the melting point and surface tension of slag, while F… - It is a powerful slag modifier, and the synergistic effect of the two can significantly reduce the viscosity of high-FeO vanadium slag, greatly improving its fluidity. The improved slag fluidity creates favorable kinetic conditions for the aggregation, growth, and settling of fine metallic iron beads (MFe) entrained in the slag back into the molten metal pool, thereby directly reducing the metallic iron content in the vanadium slag. Simultaneously, this invention avoids the excessive thickening of the slag system or negative impacts on subsequent vanadium extraction processes that may be caused by traditional calcium-based slag modifiers by strictly limiting CaO ≤ 1.5% and SiO2 ≤ 7.5% in the raw materials and finished product. The high TFe content (≥ 55%) in the finished product ensures its basic function as a coolant, while the specific Na2O and F... - The content range is the guarantee for achieving mild and efficient slag conditioning.

[0030] By innovatively combining the modified cold-solidified pellets of the above-mentioned specific components with the "periodic vanadium extraction-slag dumping" process, especially by concentrated addition during the slag discharge furnace, the properties of the final slag can be systematically optimized while ensuring the efficiency of the main vanadium extraction line, thereby achieving the goal of stably and significantly reducing the TFe and MFe content in vanadium slag.

[0031] The following specific embodiments will be provided to explain the solution of the present invention. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0032] Example 1: Preparation of modified cold-fixed spheres Take 75 parts of iron oxide scale (CaO 0.4%, particle size ≤3mm), 10 parts of vanadium extraction sludge (TFe 62%, CaO 0.4%, P 0.08%, H2O 25%), 3.5 parts of recycled cryolite (F 48%, Na2O 31%, Al2O3 27%, H2O 0.3%, particle size ≤3mm), and 2.0 parts of binder. After mixing evenly, press into elliptical pellets with a particle size of 40±5mm, and then air-dry naturally for 5 days to obtain the finished modified cryo-solid pellets.

[0033] Its composition, as determined by testing, is: TFe 51.5%, Na2O 4.6%, F - 6.9%, CaO 1.2%, SiO26.8%, S 0.05%.

[0034] Example 2: Preparation of modified cold-fixed spheres Take 78 parts of iron oxide scale (CaO 0.4%, particle size ≤3mm), 8 parts of vanadium extraction sludge (TFe 62%, CaO 0.4%, P 0.08%, H2O 25%), 3.2 parts of recycled cryolite (F 48%, Na2O 31%, Al2O3 27%, H2O 0.3%, particle size ≤3mm), and 1.8 parts of binder. After mixing evenly, press into elliptical pellets with a particle size of 40±5mm, and then air-dry naturally for 5 days to obtain the finished modified cryo-solid pellets.

[0035] Its composition, as determined by testing, is: TFe 52.9%, Na2O 3.23%, F - 4.4%, CaO 1.0%, SiO27.0%, S 0.06%.

[0036] Example 3: A method for reducing metallic iron in vanadium slag from a converter, using a complete operation cycle of three furnaces, where the third furnace is the slag-discharging furnace. The specific steps are as follows: The first and second heats (non-slag-tapping heats) are operated as follows: Vanadium-containing molten iron is added sequentially, with each heat weighing approximately 142 tons. In each non-slag-tapping heat, 7 tons of pig iron blocks are added to the converter as the main coolant, and approximately 25-30 kg / ton of ordinary chilled pellets are added according to the molten iron temperature. Pure oxygen blowing is performed for approximately 6.5 minutes, controlling the final temperature at around 1380℃. After blowing, the steel is tapped, and the slag is retained in the converter to provide a slag base for the next heat. The ordinary chilled pellets are conventional iron oxide pellets, mainly used for cooling and temperature control.

[0037] The third furnace (slag tapping furnace) operation: 142.5 tons of vanadium-containing molten iron (V 0.313%) were added at a temperature of 1334℃. No pig iron blocks or other metal materials were added. Within 2.5 minutes after the start of oxygen blowing, the modified chilled pellets prepared in Example 1 were added at a rate of 40.2 kg / ton of molten iron. Blowing process: Low lance position operation was adopted, with the lance positioned at 1.7m; bottom blowing nitrogen was used at a flow rate of 80 Nm³. 3 / h; oxygen supply pressure 0.75 MPa, flow rate 17500 Nm³ / h 3 / h; oxygen blowing time 6.4 minutes. Final temperature 1395℃. After blowing, semi-steel is discharged first, followed by vanadium slag.

[0038] The resulting semi-steel composition was: C 3.11%, V 0.030%; the resulting vanadium slag composition was: V₂O₅ 15.2%, P 0.045%, TFe 26.4%, MFe 13.6%. Before using modified pellets, under similar conditions, the MFe content in vanadium slag could reach about 18%, and TFe was often above 30% (of which the iron oxide content was about 12-15%). In this embodiment, by using specific modified cold-solidified pellets, the MFe content and TFe were significantly reduced, and the iron loss in the slag was significantly reduced.

[0039] Example 4: A method for reducing metallic iron in vanadium slag from a converter, using a complete operation cycle of three furnaces, where the third furnace is the slag-discharging furnace. The specific steps are as follows: The operation of the first and second furnaces (non-slag-discharging furnaces) is the same as in Example 3.

[0040] The third furnace (slag tapping furnace) operation: 141.7 tons of vanadium-containing molten iron (V 0.334%) were added at a temperature of 1275℃. No pig iron blocks or other metal materials were added. Within 3 minutes after the start of oxygen blowing, the modified chilled pellets prepared in Example 2 were added at a rate of 27.5 kg / ton of molten iron. Blowing process: Low lance position operation was adopted, with a lance position of 1.8m; bottom blowing nitrogen was used at a flow rate of 70 Nm³. 3 / h; oxygen supply pressure 0.72MPa, flow rate 17000Nm³ / h. 3 / h; oxygen blowing time 6.0 minutes. Final temperature 1405℃. After blowing, semi-steel is discharged first, followed by vanadium slag.

[0041] The composition of the obtained semi-steel is: C 3.08%, V 0.029%; the composition of the obtained vanadium slag is: V2O5 16.5%, P 0.042%, TFe 24.9%, MFe 12.1%.

[0042] Comparative Example: This comparative example uses conventional single-furnace operation and ordinary cold-pressed pellets, without employing the periodic modification process of this invention.

[0043] 141.5 tons of vanadium-containing molten iron (V 0.30%) were added at a temperature of 1294℃. 8 tons of pig iron blocks and ordinary chilled pellets (composition: TFe 58%, CaO 2.5%, SiO2 10.5%, with no intentionally added Na or F) were added to the converter at a rate of 34.6 kg / ton of molten iron. Blowing was then carried out, with the lance position and oxygen supply system following standard procedures. The oxygen blowing time was 5.7 minutes, and the final temperature reached 1386℃. After blowing, semi-steel was simultaneously discharged and slag was removed.

[0044] The semi-steel composition is: C 3.16%, V 0.030%. The resulting vanadium slag composition is: V₂O₅ 14.8%, P 0.038%, TFe 32.1%, MFe 15.5%. In this vanadium slag, the MFe content is as high as about 15.5%, the iron oxide content is about 16.6%, the total iron content is high, the iron loss is large, and the vanadium grade is low.

[0045] A comparison of Examples 1 and 2 with the comparative examples shows that using the specific component-modified cold-solidified pellets provided by this invention, combined with the "periodic vanadium extraction-slag dumping" process (concentrated use in each slag tapping furnace), can stably reduce MFe in vanadium slag to 12.1-13.6% and TFe to 24.9-26.4%, significantly better than conventional processes (MFe 15.5%, TFe 32.1%). Simultaneously, the vanadium slag grade is improved, achieving the dual objectives of reducing iron loss and improving vanadium slag quality.

Claims

1. A modified cold-solidified pellet for reducing metallic iron in vanadium extraction slag from a converter, characterized in that, Based on the total mass of the modified cold-fixed spheres, their chemical composition satisfies: TFe ≥ 50%, Na₂O 3.0~6.0%, F - ≥1.0%, CaO≤1.5%, SiO2≤7.5%, S≤0.1%.

2. The modified cold-fixed pellets according to claim 1, characterized in that: The particle size of the modified cold-fixed balls is 30~50mm.

3. The method for preparing the modified cold-fixed spheres according to claim 1 or 2, characterized in that: 65.0-80.0 parts by weight of iron oxide scale, 5.0-15.0 parts by weight of vanadium extraction sludge, 3.0-4.0 parts by weight of recycled cryolite, and 1.5-2.5 parts by weight of binder are mixed, pressed, and cured to obtain the modified cold-cured ball.

4. The preparation method according to claim 3, characterized in that: The iron oxide scale contains ≤0.5% CaO by mass and has a particle size ≤5mm. The vanadium extraction sludge contains ≥60% TFe, ≤0.5% CaO, ≤0.1% P, and ≤30% H2O by mass. The recycled cryolite contains ≥45% F, ≥29% Na2O, ≥25% Al2O3, and ≤0.5% H2O, and has a particle size ≤3mm.

5. The preparation method according to claim 3, characterized in that: The curing process involves natural air drying for 4-5 days, ensuring that the moisture content of the resulting modified cold-fixed balls is ≤3.0% and the pulverization rate is ≤10%.

6. A method for reducing metallic iron in vanadium extraction slag from converters, characterized in that: Vanadium extraction operation is carried out in two or three consecutive furnaces as one vanadium extraction-slag removal cycle, wherein the last furnace of the cycle is the slag removal furnace and the remaining furnaces are non-slag removal furnaces. In the non-slag-removing furnace cycle, pig iron blocks and ordinary chilled pellets are added to the converter and pure oxygen blowing is carried out. After the blowing is completed, the steel is tapped and the slag is retained. In the slag-removing furnace, no pig iron blocks, waste slag, or other metal materials are added. The modified cold solidified balls as described in claim 1 or 2 are added to the converter and pure oxygen blowing is carried out. After the blowing is completed, the semi-steel is discharged first, and then the vanadium slag is poured out.

7. The method according to claim 6, characterized in that: In the non-slag-discharging furnace, the amount of pig iron blocks added is 6 to 8 tons per furnace; the amount of ordinary chilled pellets added is 15 to 35 kg / ton of molten iron.

8. The method according to claim 6, characterized in that: The final blowing temperature of the non-slag-discharging furnace is controlled at 1360~1400℃.

9. The method according to claim 6, characterized in that: In the slag tapping furnace, the amount of modified chilled pellets added is 25-45 kg / ton of molten iron, and all of them should be added within 3 minutes after the start of oxygen blowing.

10. The method according to claim 6, characterized in that, The blowing process of the slag-blowing furnace meets the following requirements: oxygen lance position 1.6~2.0m; bottom-blowing gas is nitrogen, with a flow rate of 60~100 Nm³. 3 / h; oxygen supply pressure 0.68~0.85MPa, oxygen supply flow rate 16800~18500Nm 3 / h; oxygen blowing time 3.5~9.0 minutes; control the final blowing temperature to 1380~1410℃.